This invention relates to electromagnetic radiation devices in general and more specifically to a reflector system for use with doppler-based radar.
Doppler-based radar is used primarily by public law enforcement agencies for the purpose of gathering data, usually velocity, about an automobile where visual observation is inexact and impractical. The underlying concept behind doppler-based radar is that movement of an object can be detected by radiating the object and measuring the frequency of the reflected waves, calculating the difference between emanating and reflected wave frequency, determining the frequency shift and then correlating frequency shift with velocity. Devices which utilize radar and corner-cube reflectors are shown in the prior art and patents such as U.S. Pat. Nos. 2,432,984; 2,452,822; 2,697,828; 3,308,464; and 4,370,654. Corner-cube reflectors specifically and radar technology in general are well-described in the book, "Radar Principles for the Non-Specialist, Second Edition" by John C. Toomay, ISBN 0-442-20719-0.
Sometimes it is desirable to preclude this gathering of information, and thus it is desirable to inhibit or interfere with such use of this radar. Moreover, the return signal should not be actively generated. Finally, the presence of the radar may be detected by other devices in order to signal the presence of radar in order to either manually or automatically initiate operation of the system of this invention.
Thus, it is an object of this invention to provide a reflective device which inhibits or interferes with doppler-based radar speed measurement equipment.
Another object of the invention is that the apparatus should be passive in the sense that it emits no microwave energy.
Yet another object of the invention is that the device should be a reflector and not create any new signals.
These and other objects of this invention will become apparent from the following disclosure and appended claims.